Floating roof for liquid storage tanks



1945' J. H. WIGGINS 2,386,022 FLOATING ROOF FOR LIQUID STORAGE TANKS F1168 Jan. 27, 1944 INVENTOR;

OHN H. W/ G/NS By {W ATTORNEY Patented Oct. 2, 1945 UNITED STATES PATENT orncs mama noorgziifroum sroaaca John rnwmim, amalgam. Application January 27, 1944, Serlal No. 519,959

1 claim.

This invention relates to floatingtank roofs. and is an improvement on the floating root disclosed in my prior U. S. Patent No. 2,321,058,

Figure 1 of the drawing is a vertical transverse sectional view of a floating root constructed in which drains into same from the center pontoon and from the portion of the deck located between said trough and the peripheral pontoon. In order to insure efllcient drainage 01 said trough, through the outlet leading from same, the center pontoon is arranged slightly on? center, with relatlon to the center of the roof, so that the buoyant forces exerted by the center pontoon on the deck will-tip the deck slightly, or cause the portion of the deck that constitutes the bottom or the water-collection trough to be maintained in a slightly higher position at one side of the trough, than at the other side of the trough from which the outlet leads, whereby the water in said trough will have a natural tendency to flow to the outlet or discharge opening of the trough.

The main object of my present invention is to provide s, floating roof ofthe general kind disclosed in my said prior patent, whose component parts'are constructed or arranged in a novel.

manner, that simplifies the procedure of erectin the roof, reduces the cost of the roof, and insures perfect drainage of the water-collection trough, even in a roof of relatively great diameter.

In the roof which constitutes my present 'invention the center pontoon is arranged at the center of the roof, instead of being arranged oi'f center, as described in my said prior patent, and a small, inexpensive pontoon is attached to the underside of the deck, near the center pontoon, and at a point substantially opposite the discharge opening of the water-collection trough, so as to tilt the deck slightly, and thus maintain the water collection trough surrounding the center pontoon in such a condition or position as to insure efliclent drainage of same. In large size roofs, for example, roofs having a diameter in excess of approximately 90 it., I prefer to stiffen the deck in proximity to the center pontoon, so as to eliminate the possibility of this part of the deck sagging, and producing a flat spot in the water-collectiontrough that interferes with the drainage of said trough.

accordance with my present invention;

Figure 2 is a fragmentary top plan view of said root; and

Figure 3 is an enlarged fragmentary top plan view, illustrating the preferred method of attaching the stiflening members to the underside of the deck.

In the drawing, A designates the tank, X designates the liquid in the tank, 3 designates the deck, C designates the peripheral pontoon at the edge of the root from which the deck slopes downwardly towards the center of the roof, and D designates the center pontoon which is arranged at the center of the roof. At one side of said center pontoon a smallauxiliary pontoon E is attached tothe underside of the deck at a point substantially diametrically opposite a drain or outlet I that leads from an annular watercollection trough, designated as an entirety by the reference character formed by the portion of the deck 3 surrounding the center pontoon or -immediately adjacent said center pontoon. The

outlet I of the water-collection trough 1 may be of any preferred type or kind, and if desired, the

roof may be provided with one or more auxiliary drains 2 located between the peripheral pontoon C and the water-collection trough y, as disclos in my previously mentioned patent.

when the roof is floating on the liquid in the tank, the buoyant force of the auxiliary pontoon E lifts one side of the center pontoon D, with the result that the water-collection trough y is tilted slightly and maintained in such a condition or position, that said trough has a down slope throughout its entire area from its high side (where the auxiliary pontoon E is located) to its low side, from which the drain device I leads. By arranging the pontoon D at the center of the roof, instead of off center, and using a small, inexpensive auxiliary pontoon E to tilt or raise One side of the portion of the deck immediately adjacent the center pontoon, I produce a roof that is just as efflcient as a roof of the particular construction illustrated and described in my said prior patent, but which is easier to build or erect. As previously stated, the auxiliary pontoon E is small and inexpensive. For example, on a roof having a diameter of it. an auxiliary pontoon E having a diameter of approximately 6 ft., and a depth of approximately 3 it., will tip the rim of the center pontoon from 4 to 5 inches, which is suillcient to insure proper drainage of the watercollection trough 1!. Due to the iactthat the 2 assaoas portion or the deck bridging the space between the peripheral pontoon and center pontoon is limber, the tipping oi the peripheral pontoon is tel-pontoon, and thus producing a ilat' spot in.

the water-collection trough 11 that might interi'ere with the proper drainage of said trough. Usually, the stiilening members 3 will start a short distance away from the peripheral edge of the center pontoon, say, for example, 6 to 10 inches, and will extend radially to a point, say. approximately one-third-way the portion of the deck that bridges the space between the peripheral pontoon and the center pontoon, a sumcint number of said stiflening members being used to maintain the trough portion of the deck in an inclined position sloping downwardly to the peripheral edge of the center pontoon. In addition to maintaining the deck in a downwardly sloped position, the stifiening members 3 decrease the total water load on the roof by preventing the deck from sagging when loaded. The stiflening members 3 do not have to be very strong, nor very long. The maximum load they have to carry is a portion of the weight of the plate and any water load. Even in largest size roots, the stiflening members 3 need be only about 8 it. long. They can consist of light weight beams, and accordingly, are inexpensive and add very little to the weight of the roof.

It is immaterial how the stifiening memberst are attached to the deck, but I prefer to weld them to the deck and arrange them on the underside o! the deck so that they are out of sight, they require no painting, and they will not constitute obstructions on the top side or the roof that are liable to catch rust and dirt that falls onto the root from the tank side wall. One convenient and inexpensive way of attaching the stiflening members 3 to the deck is to provide the members I with lugs! that are adapted to be inserted in holes in the deck, and'then secured in position by welds which close the holes in the deck that receive the lugs I and also'securely attach said lugs to the deck. This method per,- mlts the stiflening members 8 to be attached to the deck by welding operations, performed from the top side of'the deck, and also enables said stifl'ening members to be attached to the deck while the deck is still on its erection framing and held in the proper slope.

Having thus described my invention, what I clatiiiis as new and desire to secure by Letters Paten A floating root for liquid storage tanks, comprising a still! peripheral pontoon, a stiff center pontoon arranged in spaced relation with said peripheral pontoon, a deck attached to said pontoons so as to bridge the space between the same and sloping downwardly and inwardly towards the center pontoon, the periphery of said center pontoon projecting above the deck and the portionof the deck surrounding saidcenter pontoon, constituting an annular water collection trough provided with an outlet, and a buoyant means consisting of a small auxiliary pontoon attached to the underside of the deck at one side only of said center pontoon at a point substantially diametrically opposite the outlet of said water collection trough, for maintaining the deck in a position to'ins'ure efiicient drainage of said trough.

JOHN H. WIGGINS. 

